Pressure-gage.



F. CONRAD.

PRESSURE GAGE.

APPLICATION FILED JUNE 9,1910.

Fig. 1

WITNESSES:

Patented Aug. 17, 1915.

B g-Z llih il lflllll FATE FRANK CONRAD, OF PITTSBURGH, PENNSYLVANIA, ASSIGNOB TO WESTINGHOUSE ELECTRIC AND MANUFACTURING COMPANY, A CORPORATION OF PENNSYLVANIA.

PRESSURE-GAGE.

issuers.

Specification of Letters Patent.

Patented Aug. ll-J2,

To all whom, it may concern Be it known that I, FRANK CONRAD, a citizen of the United States, and a resident of Pittsburgh, in the county of Allegheny and State of Pennsylvania, have invented a new and useful Improvement in PressureGages, of which the following is a specification.

My invention relates to pressure gages, and it has for its object to provide a gage which is particularly useful for the nreasurement of very low pressures, such as the degree of vacuum ina chamber but which may be employed for measuring pressures of any kind and degree.

Fi ure l of the accompanying drawing is a side and sectional view of a gage that is adapted to measure pressures which are less than atmospheric pressure, and Fig. 2 is a similar view of a gage that is adapted to measure pressures which are either above or below atmospheric pressure.

The gage comprises a glass tube or reeptacle 1 that is closed, at its lower end, and is adapted to be connected, at its upper end, to the receptacle or chamber the pressure in which it is desired to measure. The receptacle is partially filled with a suitable liquid 2, such as mercury, in which is immersed a. shell or hollow body 3 that is closed at its upper end, and open at its lower end, and is preferably composed of material having a slightly less specific gravity than mercury or other liquid in which it is immersed, such, for instance, as a suitable combination of iron and platinum. The main portion of the shell 3 is very thin, and the lower end is relatively thick, in order that the changes in the amount of mercury which is displaced, as the shell rises and sinks therein, may be small, as compared with the total amount that is displaced.

Extending vertically from the respective ends of the shell 3 are rods 5 and 6 that are surroiuuled by loops on the free ends of wires 7, the other ends of which are sealed in the walls of the receptacle 1, the said wires serving to maintain the shell central within the tube or receptacle and to guide it in its movements. The rod or extension 5 carries a disk 9, or other suitable indicating device, that projects adjacent to av suitably calibrated. scale 9 which is attached to, or marked upon, the walls of the receptacle 1.

In order to adapt the gage to the measurement of pressures which are less than atmospheric pressure, for which purpose it is particularly useful, the shell 3 should be completely filled with mercury at atmospheric pressure, as shown in Fig. l, in which case, the indicator 8 will rest adjacent to the l. millimeter mark upon the scale, since the lower end of the body rests upon the lower guide wire 7. If the gage is connected, at its upper end, to a chamber in which the pressure is less than atmospheric pressure, the pressure upon the outside of the shell 3 is also less than atmospheric pressure. Accordingly, on account of the difierence in the specific gravities of the mercury and the shell, the shell will rise until the pressures within and Without it have equalized or become the same, the degree to which it rises depending, of course, upon the pressure in the upper part of the receptacle 1. This pressure will be indicated upon the scale 9 by means of thedisk 8 that is carried by the shell 3. The shell 3 extends somewhat above the mercury outside of it and to such an extent that it will not rise until the pressure in the upper part of the receptacle.

mercury that is displaced by the immeised portion of the shell when the indicator 8 is at the zero mark of the scale, and, in order to provide a long scale, the portion of the shell that moves into and out of the mercury should be very thin, so that a. considerable movement thereof is necessary to materially change the volume of mercury displaced thereby. lVhen the indicator 8 is at the 1 mm. mark of the scale, there is a difference of 1 millimeter in the heights of the mercury within and without the shell, and Whenthe indicator is at the zero mark, the mercury is of the same height within and without the shell, while the difference in the several dilferent degrees of menu.

If it is desired to employ the gage for the purpose of measuring pressures both above and below atmospheric pressure, a suitable amount of air should be admitted to the shell 3, as indicated in Fig. 2, in order that the said body may be caused to sink deeper into the liquid when the ressure in the the heights varies between those limitsfor within the shell will be compressed and the body will sink until the pressures within and without are the same. The zero of the scalewill, of course, in this case, be at the middle or other intermediate point thereof, and, for donvenience, the upper part of the scale isgraduated in inches of mercury, and

the lower part is graduated in pounds of pressure per square inch, as is usual with gages employed for like purposes.

I claim as my invention:

1. A pressure gage comprising a receptacle, a liquid contained therein, an inverted cup-shaped body having its open end extending into the liquid and its other end cut off from external communication, the said body having a' slightly less specific gravity than the liquid, and means for applying the pressure to be measured to the surface of said liquid and'to the exposed surface of said body.

2. A pressure gage comprising a receptacle, a liquid contained therein, an inverted cup-shaped body having its open end extending into the liquid and its other end cut off from external communication, the said body being filled with the liquid at a given pressure, and means for applying the pressure .to be measured to the surface of said liquid and to the exposed surface of said body. a

8. A pressure ga'ge comprising a re ceptacle, a liquid contained therein, an inverted cup-shaped body having its open end extending into the liquid and its other end cut off from external communication, the said body being filled with the liquid at a given pressureand having a slightly less specific gravity than the liquid, and means forapplying the pressure to be measured to the surface of said liquid and to the exposed surface of said body.

4. A pressure, gage comprising a receptacle, a liquid contained therein, an inverted cup-shaped body having its open end extending into the liquid and its other end cut off from external communication, the main portionof the said body being thin and its lower end being relatively thick, and means for applying the ressure to be measured to the surface of sai liquid and to the exposed surface of said body.

' tending into the mercury and its other end cut off from external communication, the said body being filled with mercury at atmospheric pressure, and means for applying the pressure to be measured to the surface of said mercury and to the exposed surface of said body.

7. A gage comprising a receptacle, a

liquid contained therein, an inverted cupshaped body having its open end extending into the mercury and its other end cut off from external communication, the portion of the body that moves into and out of the liquid being thin, and means for applying the pressure to be measured to the surface of said liquid and to the exposed surface of said body.

8. A pressure gage comprising a receptacle, a liquid contained therein, an inverted cup-shaped body having its open end extending into the liquid and its other end cut off from external communication, the said body having a slightly less specific gravity than the liquid and being filled with the liquid at a given pressure, the portion of the body that moves into and out of the liquid being thin relatively to the portion that remains in the liquid, and means for applying the pressure to be measured to the surface of said liquid and to the exposed surface of said body.

In testimony whereof, I have hereunto subscribed my name this 26th day of May,

FRANK CONRAD. Witnesses:

PAUL MACGAHAN B. B. HINES. 

